东海陆架盆地丽水凹陷古新统物源分析及地质意义

Provenance analysis and geological significance of Paleocene in Lishui Sag, East China Sea Shelf Basin

吴柘锟 李琦 张迎朝 李风勋 覃军 单帅强 朱珍君 耿慧 陈贺贺

WU Zhekun LI Qi ZHANG Yingzhao LI Fengxun QIN Jun SHAN Shuaiqiang ZHU Zhenjun GENG Hui CHEN Hehe

中国地质大学(北京) 海洋学院，北京 100083 中国地质大学(北京) 海洋与极地研究中心，北京 100083 中海石油(中国)有限公司 上海分公司，上海 200335 中国石化 石油勘探开发研究院 无锡石油地质研究所，江苏 无锡 214126

School of Ocean Sciences, China University of Geosciences (Beijing), Beijing 100083, China Marine and Polar Research Center, China University of Geosciences (Beijing), Beijing 100083, China Shanghai Branch, CNOOC Ltd., Shanghai 200335, China Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China

东海陆架盆地古新统的物源演化是控制该地区沉积充填演化的主要因素。物源特征分析在盆地勘探开发方面具有重要意义。基于东海陆架盆地丽水凹陷古新统的取心样品开展系统的岩石学及矿物学特征分析，通过砂岩碎屑组分、轻、重矿物组合及相关参数的时空分布研究，探讨研究区古新统物源体系演化及其对盆地沉积充填的指示意义。丽水凹陷古新统碎屑岩主要为岩屑长石砂岩、长石岩屑砂岩和岩屑砂岩，砂岩以中等—较好分选为主，颗粒多为次棱角状—次圆，整体磨圆较差，指示结构成熟度和成分成熟度相对较低。古新统月桂峰组—灵峰组在盆地不同部位的轻矿物组合特征明显不同且分带性明显：西次洼中部和北部以再旋回造山带母岩类型为主；西次洼南部则以再旋回造山带和岩浆弧母岩类型为主；东次洼以再旋回造山带母岩类型为主。研究区古新统各主要层位的重矿物组合特征变化较小，西部浙闽隆皱带和东部雁荡凸起为丽水凹陷最重要的物源区，盆内灵峰低凸在明月峰组下段沉积之前遭受严重剥蚀，向盆内提供局部物源。丽水凹陷古新统的物源体系分析表明，月桂峰组—灵峰组沉积期处于盆地断陷初期—断陷高峰期，盆内断隆发育形成盆内物源区，灵峰组上段沉积时盆地开始进入断陷后期，不再发育局部盆内物源，主体以盆外物源体系为主。

The provenance evolution of Paleocene is a main factor controlling the sedimentary filling characteristics of the East China Sea Shelf Basin, and is of great significance in the exploration and development of petro-bearing basins. Based on the core samples of the Paleocene of the Lishui Sag, East China Sea Shelf Basin, the systematic analysis of petrological and mineralogical characteristics was carried out. Through the study of the spatial and temporal distribution of sandstone clastic components, light and heavy mineral assemblages and related parameters, the evolution of the Paleocene provenance system in the study area and its significance for the sedimentary filling of the basin were discussed. The Paleocene clastic rocks in the Lishui Sag are mainly lithic feldspar sandstone, feldspar lithic sandstone and lithic sandstone. The sandstone is mainly moderately well-sorted, and the grains are mostly subangular or subrounded, with poor overall rounding, indicating that the structural maturity and compositional maturity are relatively lower. The light mineral assemblages of the Guifeng and Lingfeng formations of Peleocene are obviously different and show zoning features in different parts of the basin. In the central and northern parts of the western subsag, there are mainly parent rock types of cycle orogenic belts, while in the south of the western subsag, there are mainly parent rock types of cycle orogenic belts and magma arc. In the eastern subsag, there are mainly parent rock types of cycle orogenic belts. The characteristics of heavy mineral assemblages in the main horizons of the Paleocene in the study area change little. The Zhejiang-Fujian uplift belt in the west and the Yandang uplift in the east are the most important provenance areas of the Lishui Sag. The Lingfeng low uplift in the center of the basin suffered serious denudation before the deposition of the lower member of the Mingyuefeng Formation, providing local provenance for the basin. The provenance system analysis showed that when the Yueguifeng and Lingfeng formations were deposited, they were in the early and peak stages of fault depression, and the intra-basin provenance area was formed by the intra-basin fault uplift. As the upper member of the Lingfeng Formation was deposited, the basin entered the late stage of fault depression, local intra-basin provenance was no longer developed, and the main provenance system was extra-basin provenance.

国家自然科学基金项目 41576066

https://doi.org/10.11781/sysydz202301122